Introduction: Diabetes is one of the chronic illnesses and nowadays one of the most important methods for evaluation of treatment and care is to assess the quality of life. This study aimed to investigate the role locus of control and cognitive fusion in the prediction of quality of life in diabetic patients.

Methods: The study was based on a descriptive correlation method. Statistical population consisted of all patients with type 2 diabetes in Ardabil city in 2015. 116 diabetic patients were selected as the statistical sample using the convenience sampling. Data were collected through Rotter's locus of control scale (1966), Gillanders cognitive fusion scale (2014) and the world health organization quality of life Scale (1996). Research data were analyzed by Pearson correlation coefficient and multiple regression methods.

Results: The results showed that there is a significant relationship between locus of control and quality of life in diabetic patients (r= 0.467, P=0.001). Also there is a significant relationship between cognitive fusion and quality of life in diabetic patients (r= -0.346, P=0.001). Beta coefficients for predictor variables indicated that, locus of control 0.46 (P=0.001) and cognitive fusion -0.31 (P=0.001) have significantly predictive capability of quality of life in diabetic patients.

Conclusion: Hence, it can be concluded that, locus of control and cognitive fusion are considered as the variables related to quality of life in diabetic patients and have predictive capability of it.